Wetlands are essential for purifying water, but human activity poses serious risks to many of them. This study investigates the removal efficiency dynamics of the Kotagala natural wetland in Nuwara-Eliya, Sri Lanka, which is increasingly endangered by encroachment and untreated effluent discharges. There is a need to better understand the factors influencing the efficacy of wetlands in contaminant removal under varying environmental conditions. To address this, we utilized a general removal efficiency equation to calculate removal efficiency values. Then descriptive statistics and P values were used to analysis the data statistically. Temporal analysis of removal efficiencies shows significant deviations from the general trend, particularly in the removal of phosphate and nitrate. Analysing the impact of monthly precipitation on removal efficiencies reveals a positive relationship between wet months on EC, TSS, Nitrate and Phosphate. On the other hand, salinity and TDS exhibit negative correlations with precipitation. All the p values associated with the different parameters shows the less values than significant level which is 0.05. It concludes, there is a significant relationship in between the removal efficiencies and the rainfall fluctuations. Regardless challenges, the Kotagala wetland exhibits potential for improving water quality, highlighting its importance as a natural remedy further study reveals that rainfall is not only factor influence on the nutrient removal efficiencies.